It is known in the public and to the artisan that wastes, which accumulate worldwide, represent an increasing problem with regard to environment.
For many years wastes have been disposed of by landfilling, for example in abandoned pits and remote areas. For a long time the chemical structure of wastes and their long term effects on soil and ground-water have not been taken sufficiently into consideration. During recent years hazardous wastes have been disposed of at special sites where measures have been taken to prevent leaking into the ground. In the future however also at these sites environmental contaminations are to be expected.
Consequently extensive endeavours have been undertaken in order to reprocess wastes and to obtain on the one hand improvements with regard to environmental contaminations and on the other hand useful products from wastes.
In "The Oil and Gas Journal" of Dec. 25, 1978, page 80, for example a pilot plant is described for the pyrolysis of plastics, whereby gases and fuel oils are obtained.
In "Hydrocarbon Processing", Apr. 1979, page 183, an incineration system is described, which is particularly suited for burning hazardous wastes.
Also the biochemical degradation of plastics has been investigated (see for example: European Chemical News, Sept. 10, 1979, page 28). In "Chemical Engineering", Aug. 13, 1979, page 41, the solidification of hazardous wastes is described by mixing wastes with solidifying materials like cement.
A survey of the most important processes for handling waste materials is presented in "Chemical and Engineering News", Oct. 1, 1979, page 34. Particular emphasis is laid on gasification of biomass, for example of wood and related feedstocks. Products are essentially carbon monoxide and hydrogen.
On page 36, left column, a test program is disclosed for the conversion of wood, suspended in water, in the presence of hydrogen and Raney-nickel.
In "Europa Chemie", 25, 1979, page 417, a process for the plastification and molding of mixed plastic waste is described. The fluidized bed incineration of wastes is described in "Chemische Industrie", XXXII, Apr. 1980, page 248.
The conversion of wastes and biomass by treatment with water and alkali is described in "Chemistry International", 1980, No. 4, page 20. Numerous additional publications in the field of waste treatment are known.
In recent years, in particular waste incineration has been developed and large-sized technical units have been constructed. Although dust removal and flue gas scrubbing have been integrated into these units, contaminations like heavy metals, SO.sub.2, NO.sub.x and others, escape into the atmosphere even under very advanced operating conditions. Furthermore by incineration, valuable synthetic organic materials, which are at least in part, rich in hydrogen are converted into CO.sub.2 and H.sub.2 O.
In the meantime pyrolysis is also carried out on a technical scale (see for example: "Vereinigte Wirtschaftsdienste GmbH", Oct. 4, 1985, page 9.) Disadvantages of pyrolysis are the predominant formation of gases and of considerable quantities of a strongly contaminated coke residue.
The description of the state of the art indicates that the problem of reprocessing wastes has hitherto not been solved satisfactorily.
A non-obvious, much more favorable solution to this problem compared to the state of the art in particular with regard to high yields of valuable liquid products, is disclosed in the German patent application DE-OS No. 34 42 506.3 and in the subsequent European application No. 85 11 4535.9 of the same applicant.
This invention concerns the hydrotreatment with or without catalysts, of synthetic waste materials like plastics respectively plastic mixtures, rubber, waste tires, textile wastes, industrial chemical wastes, waste oils, used oils and others, or mixtures of these materials and is carried out at pressures of 30-500 bar, preferably of 50-450 bar and particularly preferable of 50 to 350 bar, and at temperatures of 200.degree.-600.degree. C., preferably at 200.degree.-540.degree. C. and particularly preferable at 300.degree. to 540.degree. C., and at residence times of 1 minute to 8 hours, preferably of 10 minutes to 6 hours and particularly preferable of 15 minutes to 4 hours. Pasting oils can be added to the feed as well as coal, coal components, crude oil, crude oil components and residues, oil shale and oil shale components, oil sand extracts and their components, bitumen, asphalt, asphaltenes and similar materials. The feed respectively feed mixture can also be pretreated with a solvent and subsequently the extract fed to the hydrotreatment.
The process permits, after separation of inorganic components like glass, metals, stone materials and others, to convert waste materials without further separation into valuable hydrocarbons. These are C.sub.1 -C.sub.4 gaseous hydrocarbons, liquid hydrocarbons in the naphtha range, as well as middle distillates and heavy oils, which can be used as heating oils and diesel fuel. Preclassified waste materials can also be converted, in particular in such a way, that carbon containing organic wastes of synthetic origin, like for example plastics and mixtures of plastics, rubber, waste tires, textile waste, respectively mixtures of these materials and other organic synthetic wastes are at least roughly separated from the vegetable or biomass portion and subsequently submitted to a separate hydrotreatment, or combined with industrial organic wastes of synthetic origin, like coatings and paint resids or organic chemicals, wastes of industrial production units, organic synthetic shredding waste of the motor-vehicley industry, sewage sludge or used-oils or other industrial organic wastes of synthetic origin.
Other waste materials like paper, food residues, farm and wood wastes, plant residues and others can roughly be separated or remain in the synthetic portion to a certain extent.
Garbage can for example be reprocessed in such a way that plastics, rubber, textiles and other synthetic materials are roughly separated and separately submitted to hydrotreating, or combined with waste tires and/or industrial chemical and plastic waste and/or used-oils and others as described above.
The process is also very well suited for hydrotreatment of the above-named wastes resp. waste mixtures in combination (mixed) with coal, coal components like for example residual oils derived from coal, coal oils, pyrolysis oils, crude oil, residual oils derived from crude oil, other crude oil components, oil shale and oil shale components, oil sand extracts, asphalt and bitumen and similar materials, as well as with mixtures of these materials.
The separation of the above-named inorganic materials from carbon containing waste materials can be carried out according to the state of the art. These inorganic materials can be disposed of by landfill for example, if they are not recycled and reprocessed separately. Crushing or shredding and separation of waste material can be carried out according to the state of the art. If the construction of the processing devices is not prohibitive, the process can also be carried out in the presence of inorganic materials.
Waste components, which can not be converted into hydrocarbons, like for example sulfur, nitrogen, oxygen and halogens, in the form of their compounds are converted into their gaseous hydrogen compounds, i.e. H.sub.2 S, NH.sub.3, HCl, H.sub.2 O and others. These compounds can be separated by gas scrubbing and be further processing according to the state of the art.
In addition, the formation of hazardous compounds, which are obtained by waste incineration, like NO.sub.x, SO.sub.x or of dioxines is avoided according to this process. Furthermore plastics like polyvinyl chloride, which are difficult to incinerate, can be processed without risk with regard to environment.
Hydrogenation of carbon containing waste materials can be carried out according to this disclosure with very good results in the absence of catalysts. However even improved results can be obtained in particular with regard to the selectivity of formation of certain hydrocarbon fractions, in the presence of catalysts, like for example in the presence of metals and compounds, which are catalytically active in hydrogenation like for example Fe, Cr, Zn, Mo, W, Mn, Ni, Co, Pt, furthermore alkali and alkaline earthes like Li, Na, K, Rb, Pd, Be, Mg, Ca, Sr or Ba and other metals and/or their compounds, whereby these catalysts can consist of a single active component or a mixture of at least two of the components and whereby these components may be applied on catalyst carriers for example on alumina, silica, aluminum silicate, zeolites, other carriers which are known to the artisan as well as mixtures of these carriers or without carriers. Also certain zeolites and other carries are active by themselves as catalysts.
Other catalysts which can be used are so-called once-through catalysts like hearth furnace coke (Herdofenkoks), gasification dusts, for example high-temperature-Winkler dust (HTW dust), dusts and ashes obtained by the gasification of coal in the presence of hydrogen, whereby methane is formed (HKV dust), furthermore materials, which contain iron oxides, like so-called red mud, Bayer-mass, Lux-mass, dusts from the steel industry and others. These materials can be used as such or be doped with metals or metal compounds active in hydrogenation, in particular with heavy metals and/or their compounds, like Fe, Cr, Zn, Mo, W, Mn, Ni, Co, Pt, Pd, furthermore alkali und alkaline earthes like Li, Na, K, Rb, Be, Mg, Ca, Sr or Ba, as well as mixtures of these metals and/or metal compounds.
The catalysts can be sulfidized before or during use. The catalysts disclosed can be used as single components or as mixtures of at least two of these components.
The hydrotreatment can take place in wide ranges of temperature and pressure depending on the feed material namely from 200.degree. to 600.degree. C. and 30 to 500 bar at residence times of 1 minute to 8 hours.
The hydrogenating gas can be of different quality, it may contain for example besides hydrogen, certain quantities of CO, CO.sub.2, H.sub.2 S, methane, ethane, steam etc.
Suitable hydrogen qualities are for example those, which are formed by gasification of carbon containing materials. Such materials may be residues from the processing of crude oil and other oils of mineral oil origin, or coal, including lignite, wood, peat, or residues of coal processing operations as for example coal hydrogenation. Appropriate gasification materials may also be biomass and the vegetable portion of garbage. Of course pure hydrogen qualities as for example hydrogen produced electrolytically are also well suited.
Thus, for example garbage can be first separated into a vegetable and into a synthetic portion and subsequently the vegetable portion can be gasified in order to produce hydrogen to be used in the process, whereas the synthetic portion is treated with hydrogen.
According to this process also a treatment with suitable solvents, in particular hydrogen donor solvents can preceed the actual hydrogenation. Subsequently dissolved and undissolved material can be separated from each other and separately subjected to hydrogenation in the hydrogenating reactor or be introduced into the reactor as a whole. By subsequent distillation the solvent can be separated and recycled. The undissolved material can alternatively be subjected to gasification or coking.
Again in this variant the waste material feed can be mixed with coal and coal components, crude oil and crude oil components and other materials as mentioned previously.
Suitable solvents are for example tetraline, anthracene oil, isopropanol, cresols containing oils, decaline, naphthaline, tetrahydrofurane, dioxane and also other hydrocarbons from mineral oil and coal origin or hydrocarbons originating from the hydrogenating unit, as well as oxygen containing hydrocarbons and oils. Finally also water or steam can be added.
Alternatively the waste material can be first separated into a vegetable/biomass/cellulose portion and a synthetic portion and both portions can be processed separately, whereby the vegetable/biomass/cellulose portion is essentially cleaved hydrolytically, for example in the presence of bases or acids, whereby this conversion may be carried out preferentially in the presence of water and/or other protic solvents like alcohols and/or in the presence of carbon monoxide and/or hydrogen, whereas the essentially synthetic portion is hydrotreated as described above.